The delivery of drugs through the skin provides many advantages. Primarily, it is a comfortable, convenient and noninvasive way of administering drugs. Moreover, such a means of delivery provides for uninterrupted therapy and a higher degree of control over drug concentrations in the blood.
In general, it is difficult to remove a thermally cured release liner from an adhesive layer or an intermediate laminate containing polyisobutylene (“PIB”) and mineral oil without damaging the adhesive or intermediate layer. Usually, the greater the mineral oil to PIB ratio contained in the adhesive or intermediate layer, the more difficult it is to peel off the release liner. Because of this, special manufacturing processes are needed.
U.S. Pat. No. 4,201,211 discloses a transdermal delivery device comprised of a backing layer, a drug reservoir adhesive layer containing the drug clonidine, means for releasing clonidine from the reservoir, and means for affixing the patch to the skin. The patent teaches polyisobutene as an adhesive and mineral oil as a carrier for the clonidine.
U.S. Pat. No. 4,559,222 discloses a transdermal therapeutic system comprising a drug reservoir adhesive layer and an adhesive layer containing a moderately mineral oil soluble drug dispersed in the reservoir layer at a concentration above saturation. The patent also teaches a reservoir layer and an adhesive layer comprising a mixture of a mineral oil, polyisobutylene, and colloidal silicone dioxide. The patent further discloses a drug release rate controlling membrane disposed between the reservoir layer and the adhesive layer.
U.S. Pat. No. 4,832,953 discloses a scopolamine transdermal system comprising: a) a backing film; b) a drug reservoir adhesive layer comprised of polyisobutylene, mineral oil, and scopolamine base; c) a membrane layer; d) a skin contact adhesive layer comprised of polyisobutylene, mineral oil, and scopolamine base, and e) a siliconized release liner. The patent discloses a method of forming a device comprising the steps of a) casting a drug reservoir adhesive layer to a backing film to form an adhesive-backing layer laminate; b) casting a skin contact adhesive layer to a release liner to form an adhesive-release liner laminate; and c) laminating the adhesive-backing laminate and adhesive-release liner laminate to opposite sides of a membrane.
In each of U.S. Pat. Nos. 4,559,222 and 4,832,953, the drug reservoir adhesive layer is directly coated onto a backing layer. As a result, the backing film curves when the drug reservoir adhesive on backing film is dried, at an elevated temperature, in order to remove solvent.
U.S. Pat. No. 6,306,475 discloses a pressure-sensitive laminate and a method for making same, for which the release strength between an adhesive layer and a release liner can be selectively varied after the laminate has been manufactured by exposing the interface between the adhesive layer and the release liner to ultraviolet light. However, the prior art does not teach a UV-cured release liner which can be peeled off from a mineral oil containing transdermal system.
There remains the need for a release liner that can be easily peeled off from a mineral oil containing transdermal system without damage to the adhesive layer.